Storms that produce precipitation in the Midwest originate from different areas outside of the US. The location of where these storms come ashore and the position of the jet stream give meteorologists an idea of how much precipitation to expect. However, this year has been difficult to forecast because storms from multiple areas have been approaching at the same time. The meteorologists have to figure out where the storms will meet and which one is stronger to know the path and precipitation of the storms.
As shown in the image and explanations below, meteorologists have come up with names for events that occur fairly regularly throughout the winter season and cause winter storms.
Gulf of Alaska Low / Pineapple Express
A Gulf of Alaska Low is a low pressure system that originates in the maritime polar air mass of the Gulf of Alaska. Restricted by the high mountains around the Gulf, the system moves south and crosses onto land somewhere between Canada and California, continuing eastward across the Rockies. The Rocky Mountain chain greatly affects the weather patterns in the Midwest, but that will be discussed later in this article.
A Pineapple Express is “the Subtropical Pacific Jet Stream, a very moist, warm channel that has ventured further north than usual. Being tropics-born, this Pacific airstream has been linked to an origin in the vicinity of the Hawaiian Islands, the land of the Pineapple…”
When the warm, moist air from the Pineapple Express meets up with a cold Gulf of Alaska Low, it produces extreme amounts of snow.
A clipper is the style of boat built to be the fastest sailing vessels of their time in the mid 1800’s. An Alberta Clipper storm is named after these ships since it is a fast moving low pressure system that forms and descends quickly into the US from Alberta, Canada. These systems generally enter the US through Montana or North Dakota and plunge south before moving eastward. Picking up warm moisture from the Pacific Oceans and combining with the cold air in Alberta, it is forced south due to the Jet Stream. With little access to gain additional moisture, these storms typically only produce 1 to 4″ of snow. They do, however, produce strong cold winds that create some long spells of very cold weather.
Responsible for most of the major storms throughout the Midwest this past December, the Panhandle Hook, is a low pressure system that usually enters from California. It picks up warm moist air from the Gulf of Mexico and, due a south loop of the jet stream, turns northeast near the Texas and Oklahoma Panhandles towards the Great Lakes. As it passes through the cold air, it begins to dump large amounts of snow across the region.
The Colorado Low is very similar to the Panhandle Hook as it is brought northeast by the jet stream, but the low emerges from the lee of the Rocky Mountains in Colorado instead of Texas. Though still favorable for major snowfall, without the proximity to moisture from the Gulf of Mexico, it does not typically produce as much snowfall across the Midwest as the Panhandle Hook.
Rocky Mountain effect
Without the Rocky Mountain range, the low pressure systems entering the west coast of the US could continue to build in strength and wreak havoc across the Midwest. As the systems hit the Rockies, however, they are forced higher into the atmosphere where moisture content is unable to hold, and rain and snow fall onto the mountains. After passing through the mountain range, many systems are still intact, but in a much lesser form. They must rebuild in order to create a new storm on the eastern side of the mountains.